Gravity roller conveyors



Sept. 3, 1968 o. J. a. ORWIN GRAVITY ROLLER CONVEYORS 3 Sheets-Sheet 1 Filed March '7, 1967 Fl I.

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GRAVITY ROLLER CONVEYORS Filed March 7, 1967 3 Sheets-Sheet 2 [men-r02: out 1mm Qakcw 0mm 0.- 0* New Sept. 3, 1968 o. J. B. ORWIN GRAVITY ROLLER CONVEYORS 3 Sheets-Sheet 3 Filed March 7, 1967 lwemue'. out 1mm "3mm we: iwst-{ mm United States Patent 3,399,752 GRAVITY ROLLER CONVEYORS Olaf J. B. Orwin, Birmingham, England, assignor to Fisholow Products Limited, Tipton, England, a British company Filed Mar. 7, 1967, Ser. No. 621,217 5 Claims. (Cl. 19335) ABSTRACT OF THE DISCLOSURE This invention relates to gravity roller conveyors, wherein one or more of the rollers are constructed as retarding rollers so as to control the maximum rate of advancement of the load to be conveyed down the gravity roller conveyor.

BACKGROUND OF THE INVENTION 1. Field of the invention This invention relates to gravity roller conveyors of the kind, herein called the kind specified, wherein one or more of the rollers are constructed as retarding rollers so as to control the maximum rate of advancement of the load to be conveyed down the gravity roller conveyor, each retarding roller comprising a hollow cylindrical shell containing a retarding liquid and mounted for rotation about a substantially horizontal axis and having disposed therein a retarding element held against rotational movement, the outer periphery of which retarding element is provided with one or more retarding portions, the radially outermost faces of which are curved about axes eccentric in relation to the axis of rotation of the roller shell so as to provide between the cylindrical interior of the roller shell and the outer periphery of each of the retarding portions, a space for retarding liquid, the cross section of which space decreases in the direction of rotation of the roller shell so as in coaction with the liquid to effect retardation of a load advancing down the gravity roller conveyor.

2. Description of the prior art In previously known conveyors of the kind specified, the retarding liquid was a hydrocarbon oil and the retarding element comprised a central spindle held against rotational movement and provided with two radially outwardly extending diametrically opposed vanes of relatively small thickness, e.g., of the order of 3 mm. By reason of this and the fact that the outer periphery of at least one vane must at all times extend beneath the level of the oil, the volume of oil required per unit length of retarding roller is substantial, since the oil must have a depth approximately one-third of the internal diameter of the roller to provide for the outer periphery of at least one vane being always at least partially immersed in the oil.

Further by reason of the aforementioned relatively small thickness of the vanes, the presence of these does not diminish appreciably the volume of oil required by reason of the aforementioned quite substantial depth of the oil for the purpose aforementioned.

Such an arrangement is quite satisfactory where the conveyor operates at room temperature, or at temperatures not appreciably in excess of room temperature, i.e., at temperatures well below 27 C., so that the viseosity and thus the retarding effect of the hydrocarbon oil is maintained.

Under conditions where the oil temperature is around or above about 27 C., the viscosity of the hydrocarbon oil is at once so greatly reduced that its retardation effect is quite inadequate.

Although it is possible to some extent to compensate for this reduction in retardation eifect by increasing the length of the rollers, frequently the location or the layout of the conveyor does not permit of this. Accordingly, in general where it is required to operate for any appreciable period of time at temperatures which are intermittently around or above about 27 C., it is necessary to employ instead of a hydrocarbon oil as the retarding liquid, some considerably more expensive liquid such as a silicone oil, the cost of which is completely prohibitive, if a design of retarding roller involving the substantial volume of liquid per unit length is employed in accordance with the previously known arrangement aforementioned.

Although this problem of providing a satisfactory retarding roller in a gravity roller has been known to us and to the inventor named herein since prior to the year 1960, the solution of this problem has until now eluded me.

SUMMARY OF THE INVENTION I have found that this difficulty can be avoided in accordance with the present invention by forming the stationary retarding element within the rotatable roller shell as a lobed as opposed to a vaned element embodying a peripheral lobe, or a plurality of peripheral lobes spaced circumferentially around the periphery of the retarding element, with said periphery throughout the entire circumference of the retarding element being adjacent to the interior of the cylindrical roller shell, the degree of adjacency being such and the retarding element being of such solid or other imperforate construction so as not to contain therein the retarding liquid, that the major portion of the interior volume of the roller shell is occupied by the lobed retarding element as opposed to the retarding liquid, with the or each lobe having an outer peripheral face which is of convexedly curved configuration, with the axis of curvature so eccentric in relation to the axis of rotation of the cylindrical roller shell that each of said convexedly curved lobe faces converges towards the interior of the roller shell in the direction of rotation of the roller shell, with the retarding liquid within the roller shell being a silicone oil or other liquid having the required viscosity characteristic at the temperature or range of temperature of operation, the depth of the liquid within the shell being such that during operation the one lobe or at least one of the several lobes if more than one has its outer periphery immersed within the liquid.

The present invention is distinguished from the previously known arrangement above mentioned, in the following important respects:

A. The retarding element is provided with one or more lobes as opposed to vanes, which lobes by reason of their lobe-like configuration necessarily have a substantially greater volume per unit length than is the case with vanes.

B. The configuration of the lobe-like retarding element is such that the volume which it occupies is a major portion of the total volume of the roller shell interior, instead of being a minor portion as is the case with the prior arrangement.

Accordingly with the present invention, even though the interior of the roller shell might be filled with the retarding liquid to a depth comparable to that of the prior arrangement, such liquid by reason of the adjacency of the periphery of the retarding element to the roller shell is in fact only disposed in an arcua-te space of small radial thickness, e.g., 3 to 5 mm. lying alongside the inner periphery of the momentarily lowest part of the roller shell, so that the actual volume occupied by the liquid per unit length of roller for a given bore of roller shell, is very much less than is the case with the prior arrangement. Alternatively the space between the interior of the roller shell and the adjacent periphery of the retarding element may be completely filled with the liquid. Whether such space is completely or partly filled with the liquid, the saving in liquid volume obtainable with the present invention per unit length of roller for the same roller bore is of the order of 70% to 90%.

Preferably, the retarding element is provided with more than one, for example at least four, lobes spaced circumferentially therearound, the provision of these additional lobes, e.g. three additional lobes entailing the following two important effects:

(a) Further increase in the proportion of the total volume of the shell interior occupied by the retarding element.

(b) Increase for a given roller diameter and length of the retarding effect of the silicone oil or other liquid in that, during the rotation of the roller, if the roller is only partly filled with the liquid, the latter will be carried around the inner periphery of the roller shell in contact therewith so as simultaneously to be in contact with each of the lobes so that these fully co-act with the roller shell and liquid thercbetween in effecting the required retardation of the rotation of the shell.

Preferably the roller is substantially completely filled with the liquid so as to be in full contact with all of the lobes at the same time and thus ensure maximum retardation.

Where the retarding element is provided with only a single lobe, this may be arranged helically around the periphery of the retarding element.

Insofar as the retarding element is provided with one or more lobes so as to be of essentially thick form as opposed to being provided with relatively thin vanes, the entire retarding element including the lobes may be formed as a one-piece solid member, e.g. by an extrusion Or moulding operation, in a suitable plastic as opposed to metal.

Accordingly, the preseint invention permits of the following constructional advantages being achieved:

(i) Increased accuracy in the shape of the retarding element.

(ii) In the event of contact between the retarding element and the interior of the roller shell in consequence of load deflection, this is less serious in its effect than would be the case if asin the prior arrangements the retarding element is formed in mild steel, in that by forming it in a plastic, in the event of such contact occurring, the retarding element provides a bearing of low friction engagement with the interior of the roller shell, while in the event of there being any slight irregularities on the interior of the roller shell, the rotational engagement under the foregoing circumstances of the plastic retarding element body would allow the body surface to conform with the interior slightly irregular surface of the roller shell, whereby free rotation of the roller shell would not be impaired.

In accordance with a further feature of this invention, each retarding roller is mounted for controlling movement in a direction substantially perpendicular to the plane of advancement of the load to be conveyed along the length of the gravity roller conveyor, with the retarding rollers when unloaded projecting in an upward direction, perpendicular to said plane, above the adjacent freely rotatable rollers of the conveyor, the mounting for each retarding roller including means urging each roller in said' upward direction by a force proportionate to the retarding torque developed between the roller shell and the retarding element, and thus proportionate to the momentum of the advancing load on the roller conveyor.

Such a feature serves effectively to maintain the retarding roller in full pressure and thus retarding engagement with the underside of a load, even where, as is commonly the case, the underside is not truly fiat and is, e.g. as not infrequently happens of slightly concave configuration with opposite ends momentarily engaging the freely rotatable rollers. At the same time as the retarding rollers can move in a direction substantially perpendicular to said plane of advancement, they are free to move downwardly under the weight of the advancing load, so as not then to project above adjacent freely rotatable rollers, and thus inhibit the passage of e.g. a light load down the conveyor.

BRIEF DESCRIPTION OF THE DRAWINGS Various embodiments of the present invention are illustrated in the accompanying drawings in which:

FIGURE 1 is a side elevation of one form of roller conveyor embodying a plurality of retarding rollers in accordance with the present invention.

FIGURE 2 is a front view partly in cross section of one of the retarding rollers of the conveyor depicted in FIGURE 1.

FIGURE 3 is a sectional view on the line 33 of FIG- URE 2.

FIGURE 4 is an end elevation of the retarding roller depicted in FIGURE 2.

FIGURES 5 and 6 are cross sectional views of two further and alternative forms of retarding element of the retarding roller depicted in FIGURE 2.

FIGURE 7 is a view similar to FIGURE 4, depicting an alternative form of mounting of the retarding roller.

FIGURE 8 is a sectional plan view of part of a retarding roller in accordance with this invention, depicting an alternative form of mounting this on the conveyor frame.

Referring firstly to FIGURES l to 4 of the drawings, the gravity roller conveyor illustrated in FIGURE 1 comprises a main frame 6 on which is mounted for rotation about mutually parallel axes a plurality of rollers, with the rollers at one end of the frame being at a height greater than the other, to provide for gravitational advancement of the load 7 to be conveyed.

Most of these rollers, namely rollers 8, are freely rotatable in the known manner on their supports, but some of, ie the remainder of the rollers, namely rollers 9 constitute retarding rollers, each retarding roller 9 where provided being disposed between two freely rotatable rollers 8.

Each retarding roller 9 is supported from a mounting bracket 10 of substantially channel configuration, and which is secured to the conveyor frame 6.

The two upstanding arms 11 of this bracket 10 each carry a trunnion member 12 on which is pivotally supported intermediate its two ends a roller carrying lever 13 one end of each lever 13 being connected to the upper end of a tension spring 14, the lower end of which is anchored to the bracket 10, so as thereby to urge in an upward direction the opposite end 15 of each lever 13, to which is clamped in non-rotatable manner the adjacent end of roller supporting shaft 16, on which is mounted the retarding roller 9.

This retarding roller comprises a cylindrical hollow shell 17 which is preferably formed of mild steel, the opposite ends of which are supported in the conventional manner through ball or other anti-friction bearings 18 from the adjacent part of the shaft 15, with each end of the shell 17 being provided with a suitable dust excluding and oil retaining seal 19 at the outside of the bearing.

Extending between the inner side of each of the two bearings 18 is a retarding element 20 formed as a moulded or extruded plastic, so as to be of solid configuration except for a central bore to accommodate the shaft 16, on which the element 20 is non-rotatably mounted by making the shaft 16 and central bore in retarding element 20 of similar non-circular, e.g. hexagonal or square configuration.

The axial length of the retarding element 20 is only by a small amount less than the distance between the two bearings 18, while the peripheral diameter of the element is only slightly less than the internal diameter of the roller shell 17. Accordingly the volume occupied by the retarding element 20, including the part of the shaft 16 therewithin is a major proportion of the interior volume of the roller shell 17, as measured between the two bearings 18 considering the roller shellempty, with the retarding element 20 and shaft 16 removed. t

The retarding element 20 is formed peripherally on its underside with a lobe 21 having an outer convex arcuate shaped face 22, the centre of curvature of which is eccentric in relation to the axis of rotation of the shell 17. This arcuate face 22 at the underside of retarding element 20 converges towards the adjacent inner face 23 of the cylindrical roller shell, the direction of convergence being the same as the designed direction of rotation of the shell 17' as denoted by the arrow in FIGURE 3.

Thus, between these two faces 22 and 23, there is provided an oil or other retarding liquid containing space 24 of small radial thickness, e.g. /s to X (3 to 5 mm.), disposed adjacent the underside of the retarding element 20, i.e. adjacent that part of shell 17 which is momentarily lowermost, which space 24 is of diminishing cross section in the direction of rotation of the roller shell, with the mini m um'cross sectional area 25 of the space 24, of thickness less than A3", i.e. less than 3 mm., being at the lowermost position, i.e., substantially vertically beneath the central axis of shaft 16, and this minimum width space 25 which extends for the full axial length of the retarding element 20, together with the adjacent part of the converging space 24 of the associated lobe 21, accommodates the silicone oil 26 or other expensive retarding liquid which is unaffected by the elevated temperature of operation.

Where, as shown in FIGURE 3, only a single lobe 21 is provided on the underside of the retarding element 20, it is unnecessary completely to fill above the level of lobe 21 the relatively small volume between the interior of shell 17 and the retarding element 20.

In the case Where the retarding element is provided with more than one lobe 21, i.e. two or four equidistantly spaced lobes 21, as shown in FIGURES 5 and 6, with two or four associated converging spaces 24, the whole of the space between shell 17 and retarding element 20 is preferably substantially completely filled with the silicone oil or equivalent liquid, so as at all times to provide a thin layer of such liquid between each of the several lobes 21 and the adjacent interior of the roller 17.

Alternatively, in the case where more than one lobe is provided, only the lowermost lobe may at all times be immersed in the oil, and reliance may be placed on the circulatory action of the shell on the oil, tending to drag this around the periphery of the roller shell between this and each of the remaining lobes, in ensuring that the latter are effective in retarding the rotation of the shell.

Whether the roller shell is completely filled or only partly filled with the silicone oil or other liquids, it will be understood in every case that as the shell is rotated, the oil or other retarding liquid is forced through the converging space 24 and minimum area space 25 between each lobe 21 and the roller shell, in such a manner as to be continually subjected to shear forces, so that individual sections of the liquid are being continually sheared or ruptured and brought together again after such momen tary separation, so as thereby to provide by reason of the inherent viscosity of the oil or other liquid substantial retardation to the rotation of the shell 17 The above described mounting of each retarding roller 9 on the pivoted levers 13 ensures that each retarding roller is mounted for movement in a direction which is substantially perpendicular to the plane of advancement of the articles, as opposed to being free to move forwardly of the conveyor.

The arrangement is such that under the constraint of the tension spring 14 of the construction shown in FIG- URES l to 4, the upper surface of each retarding roller 9 is normally retained a short distance above the inclined plane P-P in FIG. 1, to which the upper surface of each of the freely rotatable rollers 8 are respectively tangential.

Such an arrangement ensures that even if the underside of the load to be conveyed is not quite flat, e.g. slightly concave, the retarding rollers will be engaged by the underside of the advancing load to be thereby rotated and thus effect retardation of the advancing article.

. Once the retarding roller has been engaged with and rotated by the advancing load 7, it will be maintained in pressure and thus retarding engagement with the load under the retarding couple developed between the roller shell 17 and the retarding element 20, which through shaft 16 is connected non-rotatably to the pivoted levers 13. This couple will act in a direction to urge the retarding roller 9 in an upward direction substantially perpendicular to the plane P-P, and against the weight of the advancing load momentarily supported from the retarding roller, so as to maintain the latter in full pressure contact with and thus in full retarding engagement with the underside of the load. Thus, insofar as each retarding roller 9 is biased by the associated spring 14, in a direction to bring its upper surface above the aforementioned plane P-P, the aforementioned engagement between each retarding roller and the load advancing thereover is ensured.

Even though the sprin-gs 14 are purposely formed as light springs, such retarding couple and thus the pressure between the roller and the underside of the load will increase with increase in the mass of the load, since the retarding couple developed in each retarding roller will be proportionate to the momentum and mass acceleration of the advancing load.

By consrtucting each spring 14 as a light as opposed to heavy spring, it is ensured that even with the lightest load likely to be conveyed, the retarding rollers 9 will be displaced downwardly relative to the adjacent freely rotatable rollers 8, thus ensuring that the rollers 9 do not project above the plane P-P and thus so obstruct the free passage of an advancing load of small mass, as possibly to stop its advancement altogether.

An alternative method of mounting the retarding rollers 9, which ensures that the rollers are maintained in full pressure cont-act with an advancing load including a heavy load possessing considerable momentum and/or considerable acceleration, is depicted in FIGURE 7, in which each end of the roller shaft 15 is supported on a scroll cam 27, having a toothed periphery 28, which engages with a stationary toothed rack 29. The shape of the scroll cam is such that the shaft 15, together with the roller 9, is displaced angularly from the full line position into the chain line position and through a small distance which is proportional to the angle through which the cam 27 turns, under the couple developed as above described, by an advancing heavy load between the roller shell 17 and the retarding element 20.

Thus even with a heavy load the retarding rollers are maintained in full pressure engagement with the underside of the load.

In FIGURE 8 is depicted a further method of mounting the retarding rollers 9, which is similar to that shown in FIGURES 1 to 4, except that the tension spring 14 is replaced by a helical coiled spring, one end of which is anchored to one end of each of the levers 13, and the other end of which is anchored to an adjacent part of the mounting bracket 10.

With any of the above described constructions, the roller shell 17 may, as shown in FIGURE 2, have mounted thereon a non-metallic ring 30, which rotates with the roller shell, and which may be provided for the purpose of avoiding damage to the underside of certain types of advancing loads.

Also, instead of forming the retarding element 20 of each retarding roller as a one piece moulding or extrusion, it may be formed as a series of similar moulded discs secured in end to end axially aligned mutually abutting relationship with their non-circular bores engaging non-rotatably with the non-circular shaft 15.

I claim:

1; In a gravity roller conveyor, a retarding roller comprising a stationary shaft fixed to the conveyor structure, a closed ended cylindical shell, engageable with the underside of the load to be conveyed, means mounting said shell for rotation about said shaft, a lobed member fixed to said shaft and housed within said shell, said lobed member occupying the major part of the interior volume of the shell and having at least one lobe having an outer peripheral convexedly curved face which in the direction of rotation of the shell by the conveyed load converges towards the interior of the shell into a lobe tip spaced from the shell interior by a distance less than one-eighth inch over the entire width of the lobe tip, each lobe extending continuously between its periphery and the shaft in a direction radially of the shaft axis and in any radial plane containing said shaft axis, and a retarding liquid having retarding viscosity at elevated temperature completely filling the scape between each lobe tip and the interior of the shell.

2. A gravity roller conveyor according to claim 1 wherein the lobed member is provided with a single lobe the convexedly curved periphery of which extends over substantially the entire peripheral surface of the lobed memher.

3. A gravity roller conveyor according to claim 1 wherein the lobed member is provided with a plurality of lobes, the convexedly curved peripheral surfaces of '8 which collectively extend around the entire periphery of the lobed member.

4. A gravity roller conveyor according to claim 1 wherein the retarding roller is mounted for controlled movement in a direction substantially perpendicular to the plane of advancement of the load along the conveyor with the retarding roller When unloaded projecting in an upward direction perpendicular to said plane, above adjacent freely rotatable rollers of the conveyor, the mounting for the retarding roller including means urging the retarding roller in said upward direction by a force proportionate to the retarding torque developed between the roller shell and the lobed member.

5 A gravity roller conveyor according to claim 1 wherein each end of the shaft is supported on a scroll cam having a toothed periphery, which engages with a stationary toothed rack, the shape of the scroll cam being such that the retarding roller is displaced in an upward direction by a distance proportional to the angle through which the cam is turned under the retarding torque developed between the roller shell and the lobed member.

References Cited UNITED STATES PATENTS 2,618,370 11/1952 Orwin 193-35 ANDRES H. NIELSEN, Primary Examiner. 

